Grinding machine



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GRINDING MACHINE Filed Sept. 28, 1944 15 Sheets-Sheet 1 m0 HQ. Guam/her@rzhkmarm May 31, 1949. e. BRINKMANN 2,471,406

GRINDING MACHINE Filed Sept. 28, 1944 15 Sheets-Sheet 2 WW Gaemker624110770 1'? M; W 01% TTO W y 31, 1949. G. BRINKMANN 2,471,406

GRINDING MACHINE Filed Sept. 28. 1944 l5 Sheets-Sheet 3 Gaza/J72)"firm/0970171 (5', W; W d o-$ 1- y 1949. G. BRINKMANN 2,471,406

GRINDING MACHINE Filed Sept. 28, 1944 15 Sheets-Sheet 4 m Gaze/1Mgym/Wan) TOK EL May 31, 1949. cs. BRINKMANN GRINDING MACHINE l5Sheets-Sheet 5 Filed Sept. 28, 1944 .J z fiwm o o MM w 7. 1 m w k 2 JN6, L w wm Q M i w m n m 2T M U" 2 6 6 a T 4 5 4 .L M 5 2 i May 31,1949. G. BRINKMANN 7 GRINDING MACHINE Filed Sept. 28, 1944 15Sheets-Sheet 6 May 31, 1949. G. BRINKMANN 2,471,406

GRINDING MACHINE Filed Sept. 28, 1944, 15 Sheets-Sheet v a l! 79 7a 4wem /ger gram mam 6A TTO @YJ y 1949. e. BRINKMANN 2,471,406

GRINDING MACHINE Guefiflyer grin/(mam 4 MW, W, zug k May 31, 1949. G.BRINKMANN GRINDING MACHINE l5 Sheets-Sheet 9 Filed Sept. 28, 1944 Que)2772 5 rmxmyamy fig 4 14, wag/646111741 TTOw y 1949. e. BRINKMANN2,471,406

GRINDING MACHINE Gaze/72972) grz'nkwazm W 10% May 31, 1949.

Filed Sept. 28, 1944.

G- BRINKMANN GRINDING MACHINE l5 Sheets-Sheet 11 w N N Guenf/yer 5kin/02701717 May 31, 1949. G. BRINKMANN 2,471,406

GRINDING MACHINE Filed Sept. 28,-1944 l5 Sheets-Sheet l2 IIIII N V E- NT O Gaenf/rer gran/ 07 41074 aw. 09 7; M4 K7 'r'ro fi y 1949.' G.BRINKMANN 2,471,406

GRINDING MACHINE Filed Sept. 28, 1944 15 Sheets-Sheet 13 WW Que/21kgErin/077cm) fl M W 40% May 31, 1949. G. BRINKMANN GRINDING MACHINE l5Sheets-Sheet 14 Filed Sept. 28, 1944 J w ZQA- ZOLIFDQIH 3.1

hNNQH I NVENTOR. Guezziker Bruz/rma/m M I WW 6; I flier/2g? May 31,1949. G. BRINKMANN GRINDING MACHINE Filed Sept. 28,1944

15 Sheets-Sheet 15 I o w-vomumv Patented May 31, 1949 GRINDING MACHINEGuenther Brinkmann, Detroit, Mich., assignor to .Ex-Cell-O Corporation,Detroit, Mich., a corporation of Michigan Application September 28,1944, Serial No. 556,114

23 Claims. 1

The present invention relates generally to improvements in grindingmachines for relief grinding no-lead multiple thread milling cutters.

Such thread milling cutters commonly have either straight or helicallongitudinal chip clearance gashes intersecting axially spaced annulargrooves to define a plurality of annular series of relieved cuttingteeth. The purpose of the present grinding machine is to relief grindthe trailing portions of the teeth back of the cutting faces, and thelongitudinal gashes and tooth grooves may be either preformed and finishground, or ground out of solid stock. In the grinding operation, thecutter blank is rotated in operative relation to a suitable grindingwheel, and a relative relieving reciprocation in timed relation to thework rotation is imparted to the blank and the wheel once for eachclearance gash during each blank revolution. A relative approach feed isimparted to the blank and the wheel during the grinding of each selectedtooth groove until the teeth are ground to depth, and then the wheel isretracted from the blank and the latter is indexed axially to locate asucceeding tooth groove in position to be ground.

One of the objects of the present invention is to provide a grindingmachine of the foregoing character having a novel cross feed mechanismwhich is automatically operable during each machine cycle to shift thegrinding wheel relatively toward and from the cutter blank in a cyclecomprising an initial rapid approach from a remote position, a grindinginfeed for an initial tooth groove until ground to final size or depth,a dwell at the end of the infeed, a partial separating or retractmovement after the dwell to permit relative axial indexing of the blank,a succession of infeed and retract movements respectively following theindexing movements for the grinding of consecutive tooth grooves, and arapid return to and stop in the initial remote position after grindingof the final tooth groove.

Another object is to provide a new and improved grinding machinehaving across feed mechanism of the foregoing character, and in which the Workblank is automatically indexed step-by-step in one axial direction andin timed relation to successive infeed movements of the grinding wheel,and returned axially to starting position upon return of the wheel intoinitial idle position, and in which the rotation of the Work blank isautomatically started at the commencement of the rapid approach of thegrinding wheel, and interrupted upon return of the grinding wheel toremote position.

A further object is to provide a new and improved grinding machine inwhich the foregoing cycle may be interrupted at the will of the operatorafter the grinding of any tooth groove to efiect the return of thegrinding wheel past the retract position into remote inoperativeposition to permit dressing of the grinding wheel.

Another object is to provide a novel switch actuator for controlling thedrive for the work spindle regardless of variation in the length of theinfeed movement.

A further object is to provide a novel cross feed mechanism which ishydraulically operated and controlled, and which more particularlycomprises a hydraulic actuator yieldably resisting each infeed movementto obtain an adjustable controlled rate of advance until interrupted bya positive stop.

Another object is to provide such cross feed mechanism in which theresistance actuator automatically becomes a positive actuator at the endof the infeed, and is operable through an adjustable predetermineddistance to provide a controlled dwell.

A further object is to provide a novel cross feed mechanism in which thechange in the approach movement between the wheel and the blank fromrapid traverse to the grinding infeed is determined by engagement of thegrinding wheel support with an intermediate stop yieldable at acontrolled rate until the support engages a positive stop determiningthe final depth of out.

Another object is to provide a new and improved hydraulic cross feedmechanism including a control orifice which has a comparatively largeflow area for metering fluid therethrough at a relatively lowdifferential pressure to control a hydraulic actuator yieldablyresisting the infeed, and which at the end of the infeed is operable tocontrol the continued movement of the actuator to provide apredetermined period of dwell.

A further object is to provide a novel hydraulic system for a cross feedmechanism having an orifice for controlling the rate of infeed and theperiod of dwell, and having means operable at the end of the dwell forautomatically bypassing the orifice to permit rapid return of thegrinding wheel into remote inoperative position.

Other objects and advantages will become apparent as the descriptionproceeds.

In the accompanying drawings,

Figure 1 is a front perspective view of a grinding machine embodying thefeatures of my invention, certain covers being removed to expose 3 theelectric panel and the gear drive for the work indexing.

Fig. 2 is a right side perspective view of the machine, a cover beingremoved to expose part of the gear drive for the work spindle.

Fig. 3 is a perspective rear elevational view of the machine, a coverbeing removed to expose a control valve forming part of the cross feedmechanism.

Fig. 4 is a left end elevational view of the Work supporting structure.

Fig. 5 is a fragmentary right end elevational view of the worksupporting structure, partially in vertical section to illustrate thework spindle drive.

Fig. 6 is a longitudinal vertical sectional view through the worksupporting structure, taken substantially along the line 66 of Fig. 4.

Fig. '7 is a fragmentary vertical sectional view of the work indexingmechanism, taken substantially along line l! of Fig. 4.

Fig. 8 is a fragmentary transverse vertical sectional view takensubstantially along line 88 of Fig. 6, and illustrating the tooth ribpick-up mechanism.

Fig. 9 is a fragmentary transverse vertical sectional view takensubstantially along line 99 of Fig. 6.

Fig. 10 is a detail sectional view taken substantially along line Illlof Fig. 9.

Fig. 11 is a fragmentary transverse vertical sectional view through thework supporting structure, and illustrating the relieving mechanism.

Fig. 12 is a detail sectional view taken substantially along line I2I 2of Fig. 11.

Fig. 13 is a fragmentary sectional view taken along line l3l 3 of Fig.11.

Fig. 14 is a fragmentary transverse vertical sectional view illustratingthe rear portion of the cross feed mechanism of the machine.

Fig. 15 is a fragmentary transverse vertical sectional view illustratingthe forward portion of the cross feed mechanism.

Fig. 16 is a diagrammatic view illustrating the cross feed mechanism andthe hydraulic operating system and control therefor.

Fig. 17 is an elevational view of a valve forming part of the hydraulicsystem.

Fig. 18 is an axial sectional view of the valve.

Fig. 19 is a diagram identifying the port connections of the valve indifferent positions of adjustment.

Fig. 20 is a vertical sectional view taken along line 2020 of Fig. 14.

Fig. 21 is a horizontal plan view taken along line 2 |2I of Fig. 20.

Fig. 22 is a diagrammatic representation of the electrical drive andcontrol for the machine. Fig. 22a is a key diagram showing therelationship of the relays and switches incorporated in Fig. 22.

Referring more particularly to the drawings, the machine constitutingthe exemplary embodiment of the invention generally comprises a machinebase I. A work supporting structure 2 is mounted across the top of thebase I at the front, and comprises an assembly of a sub-table 3 mountedon the base for longitudinal positioning adjustment, and a work support4 pivotally mounted on the sub-table for longitudinal indexing movementand transverse relieving oscillation. Mounted on one end of the support4 is a head stock supporting a work spindle 6 and a live center I. Atailstock 8 is adjustably mounted on the work support 4, and has a deadcenter 9 in alinement with the center 1. The work blank W to be groundis adapted to be mounted endwise in position for rotation on the centers1 and 9, and to be connected through a suitable drive dog (not shown) tothe spindle 6 for rotation therewith.

A relieving mechanism I0 is provided for oscillating the support 4through a selectively adjustable distance in timed relation to therotation of the work spindle 6, and may be rendered selectivelyoperative or inoperative to oscillate the support depending on whetherthe work blank W is to be ground with or without relief.

An indexing mechanism H is provided for shifting the work support 4step-by-step in one direction axially of the work spindle 6 to locatesuccessive tooth grooves consecutively in grinding position, and forreturning the support in the opposite direction into initial position atthe end of the grinding operation. Associated with the indexingmechanism H is a pick-up mechanism 52 for locating the work blank, andparticularly the initial tooth groove, in proper position to be ground.A phase control mechanism I3 is interposed in the spindle drive, and maybe set selectively to adapt the machine for the grinding of workpieceshaving either straight or spiral gashes.

Mounted on the top of the base I (see Fig. 16) toward the rear is asuitable wheel dressing mechanism It. A tool supporting structure I5 ismounted on the base I alongside the dressing mechanism, and comprises across slide l6 mounted for movement transversely of the work spindle 6and at the front supporting a tool spindle H with a suitable grindingwheel G. The cross slide 3 is provided with a dresser feed mechanism I9,and is translatable between opposite limit positions by a hydraulictransmission forming part of a cross feed mechanism 20.

The cross feed mechanism 20 is operable to translate the cross slide 16automatically in a cycle comprising a rapid approach from a remotedressing position, a forward feed from an adjustable intermediate pointto advance the grinding Wheel G gradually into the work to final size ordepth, a dwell at the end of the infeed, and at the end of the dwell aretract movement to clear the grinding wheel G from the work so as topermit indexing of the next tooth groove into grinding position. Theinfeed and partial retract movements are repeated for all of the toothgrooves of the work blank, and after the last groove has been ground tofinal depth, the cross slide is returned without interruption to itsremote position wherein the grinding wheel may be dressed, and theindexing mechanism II is reversed to return the work spindle 6 intoinitial position for unloading and reloading.

WORK SUPPORTING STRUCTURE The sub-table 3 constitutes the base of thework supporting structure 2, and is formed along opposite sides withparallel longitudinal guideways 2i engaging suitable guides 22 on thetop of the base I. To provide means for adjusting the position of thesub-table 3, a longitudinal gear rack 23 is secured to the undersidethereof, and meshes with a pinion 24 on a stub shaft 25 journaled in andextending through the front wall of the base I. The outer end of thestub shaft 25 is suitably squared for the reception of a hand tool. Itwill be understood that the subtable 3 is adjusted only in the initialset-up of the machine to position the work blank W in proper relation tothe grinding wheel G.

Suitable clamping means are provided at opposite ends of th sub-table 3to clamp the latter in position of adjustment. Only one of theseclamping means is shown, but the two clamping means are alike inconstruction. Each comprises a clamping bar 26 extending transverselybetween and adapted for engagement underneath the guides 22. The bar 26has a vertical post 21 which extends upwardly into a bore 28 in thesub-table 3 and which is formed in one side with a tapered notch 29. Awedge member 3!] is slidably disposed in a transvers bore 3|, and has apointed end normally in wedging engagement with the upper side of thenotch 29. The wedge member 3|] is adapted to be tightened by a bolt 32threaded in the outer end of the bore 3| into end engagement therewithand accessible from the front of the machine.

The work support 4 is mounted for oscillation about, and forlongitudinal translation with, a tubular bearing member 33 slidablysupported in suitable upstanding bearing lugs or bosses 34, 35, 36 and37 on the sub-table 3. In the present instance, the lugs are formed withaxially alined bores receiving suitable bushings in which the tubularbearing member 33 is guided.- The work support 4 has two longitudinallyspaced bearing lugs 38 and 39 with inserted bushings rotatably receivingthe tubular bearing member 33. To constrain the work support 4 againstrelative sliding movement, the lug 39 is confined between a fixedperipheral collar 40 on the member 33 and a friction collar 4|. 42,seated against a fixed collar 43, acts on the collar 40 to urge thelatter against the lug 39.

The head stock 5 comprises an upstanding housing 44 formed integral withone end of the work support 4 and closed at the top by a cover plate 45.The work spindle 6 extends through the head stock longitudinally of thework supporting structure 2 and is journaled at opposite ends insuitable antifriction ball bearings 46 and 4'! mounted in opposite endwalls of the housing 44.

Work spindle drive The work spindle 6 is adapted to be driven from anelectric motor 48 mounted on the rear of the base I and connectedthrough a belt 49 to a stepped pulley 50 on the rear end of a stub shaft5|. In the present instance, the motor 48 is supported on the rear ofthe machine base for pivotal adjustment to tension the belt 49. Theshaft 5| is connected through a universal joint (not shown) to anintermediate shaft 52 extending forwardly through the base A worm shaft54 is connected through a universal coupling 53 to the shaft 52, and issuitably journaled in a depending gear housing 55 on the underside ofthe sub-table 3 within the machine base A pin 56 on the base I slidablyengages in a groove 51 in the gear housing 55 to support the latterrigidly against lateral deflection. It will be seen that the worm shaft54 is connected for rotary drive through the shaft 52 to the transverseshaft 5| in all positions of adjustment of the sub-table 3.

Fixed on the worm shaft 54 is a worm 58 meshing with a worm wheel 59 ona shaft 60 journaled in a ear housing 6| on the right end of thesubtable 3. The shaft 60 is connected through a train of speed changegears 62, 63, 84 and within the gear housing 6| to the right end of ashaft 66 extending coaxially through the tubular bear- A coiledcompression spring ing member 33. Suitable bearings 67 and 68 areprovided for supporting opposite ends of the shaft 66.

Secured to the left end of the shaft 66 is a gear 69 which meshes with agear 10 having an elongated hub rotatably and slidably supported on thework spindle 6. In the normal indexing movement of the work support 4,for example to the right, and the return movement to the left, thespindle 6 will slide axially through the gear hub 5|, the latter beingconstrained against axial movement between spaced upstanding webs orflanges l2 and 73 on the sub-table 3.

Phase control mechanism The phase control mechanism l3 serves to connectthe spindle 6 for rotary drive with the gear Ell, and is adjustable toeffect rotation of these elements as a unit when the work blank to beground has straight gashes, or to superimpose an additional rotation onthe spindle in timed relation to the axial translation when the Workblank has spiral gashes, in order to compensate for the inclination ofthese gashes and thereby maintain the spindle and the relievingmechanism I0 in correct operative relation.

The control mechanism l3 (see Fig. 8), in the form disclosed, comprisesa drive pin 14 extending transversely into a bore 75 in the spindle 6and secured in position by a set screw 16. The outer end of the pin 14is provided with an enlarged rounded spherical follower Tl separatedfrom the spindle 6 by a spacer 13. A guide plate "(9 is mounted on theflattened top of the gear hub ll for angular adjustment about a clampscrew 89, and is formed in the underside with an elongated groove lllextending generally longitudinally of the spindle 6 and slidablyreceiving the follower "ll. When the guide plate 19 is adjusted tolocate the groove 8| in parallel relation to the spindle 6, axialmovement of the latter will not alter the angular phase relation, andthe gear 10 and spindle will rotate as a unit. However, if the guideplate 19 is adjusted to locate the groove 8| selectively at an angle tothe spindle 5, the groove through coaction with the follower l1 willrotate the spindle in the gear hub ii in timed relation to the axialmovement of the spindle. In either case, the plate 79 is adjusted inaccordance with the angle of the Work gashes and, hence, is located inparallel relation to the spindle 6 for straight gashes and at anappropriate angle to the spindle for inclined gashes. The phase controlmechanism l3 is generally similar in construction and operation to thatdisclosed in copending application Serial No. 504,689, filed October 21943, by Harold N. Seyferth, now Patent No. 2,439,106, dated April 6,1948.

I ndeating mechanism The indexing mechanism (see Figs. 4 and 6) isoperative to shift the work support 4 step-bystep axially of the spindle6, through a distance in each step corresponding to the pitch of thetooth grooves of the work as the grooves are ground successively tofinal depth. In the preferred form, the indexing mechanism H comprisesan elongated lead nut 82 slidably disposed in bushings 83 within atubular guide 84 formed integrally with the left end wall of thesub-table 3. The lead nut is formed with an axial threaded bore 85 inengagement with an adjusting screw 86 suitably journaled at one end inball bearings 87. The outer end of the screw 86 is connected through atrain of speed change gears 88, 89, 90

and 9| to a stub shaft 92 suitably journaled in a bearing sleeve 93 inthe inner wall of a depending gear housing 94 on the sub-table 3. Theinner end of the shaft 92 has a pulley 95 connected through a belt 96 toan electric indexing motor 91 located within the machine base. It willbe evident that upon operation of the motor 91 in either forward orreverse direction, the screw 89 will be rotated to shift the lead nut 82axially.

The inner end of the lead nut 82 is coupled to the work support 4 fortranslation axially of the spindle 6. In the present instance, theconnection comprises a transverse arm 98 pivotally connectedintermediate its ends to the nut 82, and anchored at the inner end tothe tubular bearing member 33 for axial movement therewith. Moreparticularly, the inner end of the transverse arm 98 is keyed to themember 33 in position against a shoulder 99 by a lock nut I00.Intermediate its ends, the arm 98 is apertured to receive a reducedaxial extension Itl on the inner end of the lead nut 82. A plate I92 issecured to the end of the extension IOI by means of a bolt I03, and afriction plate I04 encircling the extension I and connected thereto by apin I85 is urged into hearing engagement with the plate I02 by aplurality of coiled compression springs I05. A wear plate I01 is boltedto one side of the arm 98 in bearing engagement with the head of thebolt I03, thereby constraining the arm 98 for movement with the lead nut82.

The forward end of the arm 98 is provided with a roller I08 riding in auide groove I09 in a bar I I0 secured to the sub-table 8 and extendinglongitudinally thereof. Thus, the arm 98 is confined against oscillationand is constrained to move axially with the lead nut 82 and the tubularhearing member 33 to shift the work support 9 upon rotation of the screw85.

Normally the lead nut 82 (see Figs. '7 and 8) is held against rotationby the pick-up mechanism I2. In this mechanism, the exterior of the feednut 82 is formed to constitute a spur gear III with elongated teeth inmesh with a skew gear II2 within a gear casing II3 formed integral withthe tubular guide 88. The skew gear I I2 is fixed on the inner end of ashaft I It which is suitably journaled in and extends through anelongated bearing sleeve II5 secured in a housing III; on the front ofthe sub-table 3. A set screw H1 is provided for securing the bearingsleeve II 5 against rotation. The outer end of the bearing sleeve H5 isformed with a flanged backing plate II8 receiving a a handwheel II9 onthe shaft H4. Upon rotation of the handwheel II9, the gear II2 willrotate the lead nut 82 to shift the work support 9, independently of theindexing drive, for pick-up or positioning of the tooth grooves inproper grinding relation to the grinding wheel G. A set screw I isprovided for locking the handwheel H9 in position of adjustment, andwhen the wheel is locked the gear IIZ acts to key the lead nut 32against rotation, while permitting axial translation thereof uponrotation of the screw 85.

In each indexing operation, the gear 9i is rotated through one completerevolution, and the train of gears 89 to 9| is selected to shift thelead nut 82 through the desired distance. The control means for thispurpose preferably comprises an index disk I 2I fixed on the shaft 92and formed in the periphery with a notch I22. Also fixed on the hub ofthe disk I2I for rotation with the shaft 92 is a cam I23 controlling aswitch LS5 through a spring-actuated follower I24. A looking plunger I25is slidably guided in a bearing bracket I25 within the housing 94 forengagement in the notch I22, and is pivotally connected by means of apin I21 toa lever I28 in turn pivoted at I29 to the bracket. One end ofthe lever I28 is connected to a coiled tension spring I30 anchored tothe wall of the housing 94 and tending to urge the plunger I25 intoengagement with the disk I2I. The other end of the lever I28 isconnected through a link I30 to the movable core ISI of a solenoid C.Mounted on the inner wall of the housing 99 is a switch LS4 having anactuating lever I32 with a roller I33 underlying the plunger I25.

In operation, upon energization of the solenoid C the plunger I25 isretracted from the index disk I2 I, thereby releasing the latter forrotation, and at the same time actuating the switch LS4 to instituteope-ration of the index motor 91. As a result, the disk I2! and the camI23 will start to rotate through one complete revolution, and willrotate the lead screw 86 to shift the work support 8 through oneindexing step. Near the end of the rotation, the cam I23 will engage thefollower I29 to actuate the switch LS5, thereby interrupting the indexmotor circuits and deenergizing the solenoid C. The motor 91 will coastto reactuate the switch LS5. Upon deenergization, the magnet C willrelease the lever I28 so as to permit the spring I30 to urge the plungerI25 into peripheral bearing engagement with the index disk I2I. Theswitch LS4, however, will remain closed until the disk I2I completes onerevolution, at which time the plunger I25 will engage the notch I22.Thereupon the switch LS9 will be opened to interrupt the circuit for thesolenoid B to effect shifting of the valve 230 into grind position forthe next infeed movement.

Relieving mechanism The work support 0 is adapted for oscillation by therelieving mechanism I0 about the tubular bearing member 33 in anyindexed position, once for each tooth, during each revolution of thespindle 8. The extent of oscillation is subject to adjustment, dependingon the desired relief. The relieving mechanism I8 may be renderedineffective when the machine is to be used for grinding work blankswithout relief, and the work support 8 may be disengaged from therelieving mechanism and swung into inoperative position to afford accessto the mechanism.

Th relieving or back-off mechanism comprises an intermediate member (seeFigs. 11 and 12) in the form of an arm I39 rotatably supported at oneend for swinging movement about the tubular bearing member 83, andconstrained against axial movement with the member 33 by the twobearings lugs 35 and 36. The forward end of the lever I39 is formed withdepending side flanges defining a guide recess I35. A cam lever I36extends rearwardly into the recess I35, and is pivoted thereinintermediate its ends, as at I31. A cam roller I38 is journaled on therear end of the lever I 38, and is in peripheral bearing engagement witha suitably contoured relief cam I39 fixed on the inner end of the shaft60.

The forward end of the lever I88 is channelshaped to constitute a radialguide I40 slidably engaged by a block MI pivotally connected by a pinI92 to an adjusting slide I43. The pin I42 constitutes an adjustablestationary fulcrum for the lever I 36. The slide I43 is suitably guidedfor adjustment transversely of the pivot I31 between parallel spacedguides I44 on the subtable 3, and is adapted to be adjusted by means ofa screw I45 rotatably anchored in the subtable, and having an adjustingknob I46 and a micrometer dial I41 on the outer end. A set screw I48 isprovided for securing the screw I45 in position of adjustment. Byadjusting the slide I43, and hence the fulcrum I42, the length of theforward moment arm of the lever I36 may be varied to adjust the throw ofthe movable fulcrum I31 and, therefore, the throw of the arm I34 by therelieving cam I39.

The intermediate member or arm I34 provides a rest for the work support4. In the present instance, a roller I49 is journaled in the forward endof the intermediate member I34, and engages an elongated wear bar I50bolted to and' extending longitudinally of the underside of the forwardportion of the work support 4. When grinding cylindrical work blanks,the bar I50 is provided with a straight track parallel to the pivotalaxis of the support. If it should be desired to grind tapered workblanks, a bar I50 with an inclined track is bolted to the work support 4as shown in Fig. 13.

A coiled compression Spring I5I is interposed between the intermediatemember I34 and the cam lever I36 to urge the roller I36 toward therelieving cam I39.

It will be understood that upon each rotation of the relieving cam I39,which is timed by the change gears 62 to 65 to complete one revolutionfor each tooth to be relieved, it will act through the lever I36 and theintermediate member I34 to oscillate the Work support 4 about thetubular bearing member 33 through a predetermined angular distance. Theextent of the relieving movement may be varied by adjusting thestationary fulcrum I42 for the lever I36.

Means is provided (see Figs. 9 and 10) for locking the work support 4 inoperative association with the relieving cam I39 when the work blank isto be relief ground, and for disassociating the work support and therelieving mechanism I when the work blank is to be ground withoutrelief. In the form shown, this means comprises a positioning lever IIwhich is rotatably supported at one end on a reduced end portion of thehub of the arm 98 for oscillation about the tubular bearing member 33.The other or forward end of the lever I5I is urged toward the arm 98 byan interconnecting tension spring I52 and is provided with a forwardlyprojecting pin I53 adapted for cooperation with a locating cam I54. Astop screw I55 is adjustably threaded through a flange on the lever I5!for engagement with the arm 93 to limit the movement of the lever inresponse to the action of spring I 52.

The cam I54 is of the annular type, and is secured axially to a, shaftI56 journaled in the front of the work support 4 and provided with ahand lever I51. The cam I54 is formed with an inner peripheral eccentriccam surface I58 and an external peripheral cam surface I59interconnected by a radial slot I60. In one position of the cam I54, theslot I60 is located in registration with the pin I53 to permit the worksupport 4 to be disengaged from the lever PSI and swung upwardly andrearwardly for the purpose of affording access to the relievingmechanism I0. Upon rotation of the cam I54 out of the release positioninto relief grinding position, the slot I60 will pick up the pin I53 andestablish engagement thereof with the inner cam surface I58. In thisposition of adjustment of the cam I54, the bar I will engage and ride onthe roller I49 and, hence, the work support 4 will be in operativeassociation with the relieving cam I39. Upon rotation of the cam I54into a third position, the external cam surface I59 will engage anadjustable stop bolt I6I in the forward end of the arm 98 to lift thework support 4 out of operative association with the relieving mechanismIII. A spring actuated detent I62 is engageable in recesses in the hubof the cam I54 to locate the latter selectively in either of the threepositions of adjustment.

TooL SUPPORTING STRUCTURE The cross slide I6 of the tool supportingstructure I5 is mounted on suitable ways I63 on the top of the base Iand extending transversely of the work support 4. Preferably a series ofball bearings are interposed between the ways I63 and the slide I6 tocomplete the bearing relationship, and to reduce sliding resistance to aminimum.

Formed on the forward end of the tool slide I6 is an upstanding housingI64. A spindle bracket I65 is adjustably secured to the front face ofthe housing I64 and supports the tool spindle I1. The spindle is adaptedto be driven at a high rate of speed from an electric motor I66 mountedon a plate I61 pivotally supported on the slide I6 at the rear of thehousing I64. The motor I66 has a pulley I68 connected by a belt I69 to apulley I10 on the spindle I1.

The tool slide I6 may be reciprocated by any suitable means, and in thepresent instance is adapted to be translated along the ways I63 by asuitable hydraulic actuator of the differential type comprising acylinder I1I mounted within and connected at one end to the rear wall'ofthe machine base I and a piston I12 reciprocable therein. The piston hasa piston rod I13 extending crosswise of the base I and anchored at itsforward end to a depending lug I14 on the slide I6. By reason of thetransverse area of the piston rod, the rod end face of the piston I 12is approximately equal to one-half of the head end face.

Fluid under pressure is adapted to be supplied through suitable passagesI15 and I16, respectively, to opposite ends of the cylinder I1I. Ashereinafter more fully described, when fluid is supplied simultaneouslythrough both passages, the piston I12 will be moved in a forwarddirection, and when fluid is supplied through the passage I15 to theforward end of the cylinder HI and exhaust fluid is displaced from therear end through the passage I16, the piston will move in a rearwarddirection.

The tool slide has three main positions of oper ation, namely, a remotelimit position in which the grinding wheel G is fully retracted from thework to permit loading and unloading, and located in position to betrued by the dressing mechanism I 4, a forward grinding position inwhich the grinding wheel is in operative engagement with the work andwhich is limited by a positive stop under the control of a size controlwheel 205, and an intermediate or partial retract position in which therinding wheel is merely retracted from the work sufiiciently to permitaxial indexing of the latter frorn' tooth groove to groove.

The rearward remote and forward operative positions of the slide I6 aredetermined by an intermediate abutment member I18 which is adjustablycarried by depending lugs I19, I80, and which is reciprocable betweenand respectively into opposite end engagement with a rear positive stop"II and a forward intermediate stop I82

